Underfilled BGAs for ceramic BGA packages and board-level reliability

Ceramic ball grid array (CBGA) packages have board-level reliability that can easily meet the needs for applications in environments with limited temperature excursions. The board-level reliability for environments with large temperature changes are frequently at the limit of what is viable for CBGA packages and occasionally not obtainable with CBGA packages. In an effort to aid board-level reliability for CBGAs, the EGA was underfilled and cycled to failure. Four different epoxies were used with four different coefficients of thermal expansion and Young's moduli. The results will be compared to a control set of non-underfilled parts. Statistical analysis for the underfilled results will allow one to determine which set of parameters provides a basis for creating extended reliability for CBGA packages. Non-linear finite element modeling will supplement the experimental work.